Akihabara@DEEP (2006)

Both have this otaku-culturish thing with otaku characters solving their problems...

It has the same moments of randomness and is very hilarious.

Both are based off the same novel. The TV drama is a lot lighter than the movie. Both are great but the movie follows the novel a bit more. Also, actors are different. I recommend watching the tv show before the movie.

The Original Novels both of these stories are based on were written by Ira Ishida. There are a lot of similarities in terms of atmosphere and setting, by the method of which the districts of Ikebukuro and Akihabara are given unique personalities. Both of these stories are urban mysteries where the protagonists investigate various crimes occurring within the city.